Diorganotin compounds

Physica.1 Properties. Physical properties of some typical diorganotin compounds are shown in Table 6. The diorganotin chlorides, bromides, and iodides are soluble in many organic solvents and, except for dimethyltin dichloride, are insoluble in water. 

Diorganotin esters of strong acids are relatively stable to hydrolysis under neutral conditions, but generally, diorganotin compounds ate more reactive chemically than the triorganotins. Diorganotin esters of weak acids are somewhat susceptible to hydrolysis, even under neutral conditions, but this reactivity is moderated somewhat by their hydrophobicity. 

Some diorganotin compounds, eg, the alkoxides, add to heterounsaturated systems, eg, isocyanates. This reaction is beheved to occur in stages... 

Prepa.ra.tlon, Diorganotin dichlorides are the usual precursors for all other diorganotin compounds three primary methods of manufacture are practiced. Dibutyltin dichloride is manufactured by Kocheshkov redistribution from cmde tetrabutyltin and stannic chloride and usually is cataly2ed with a few tenths of a percent aluminum trichloride ... 

Table 11. Acute Oral Toxicities of Diorganotin Compounds...

Bis(tributyltin) oxide is known to break down to inorganic tin under UV irradiation in laboratory conditions (509, 510), and the decomposition may be accelerated by absorbing the organotin compound on a cel-lulosic matrix (511). As bis(tributyltin) oxide is known to react rapidly with carbon dioxide (atmospheric, or trapped in various cellulosic materials, such as cotton or wood) (512), to form bis(tributyltin) carbonate, (BusSnO)2CO, the observed UV degradation pattern may be rationalized in terms of more-ready breakdown of the carbonate than of the oxide, due to the presence of the carbonyl chromophore. The half-life of bis(tributyltin) oxide in pond water has recently been given as 16 days (513). Diorganotin compounds have also been shown to decompose to inorganic tin under UV irradiation (514, 515). 

In addition, data are available for a study on the degradation of dimethyl-, dibutyl-, and dioctyltin chlorides in soil (Terytze et al, 2000). It is of note that the results of the degradation testing indicate that the diorganotin compounds are partially degraded to the corresponding monosubstituted compounds by way of example, dioctyltin concentrations were observed to decrease from 40 to 12 ng/1 over a 3-month period while the monooctyltin concentration stayed relatively constant at around 2 ng/1. It is therefore likely that only a fraction of dioctyltin decayed to monooctyltin and/or the... 

FIGURE 5. Common configurations of diorganotin compounds with bidenate ligand (a) mononuclear and (b) SnOSnO four-membered ring dimer... 

The reaction of triorganostannyllithium compounds with SnCl2, SnCLt or with triorgan-otin or diorganotin compounds has wide applications. 

Spiro stannyl complexes can be prepared116 from tetraalkynyltin compounds Sn(C=CR)4 (R = Me, Et, n-Pr, i -Pr, n-Bu) upon reaction with BEt3. This synthesis route involves a TT-coordinated diorganotin compound, 72, as an intermediate which, upon heating in toluene, gives the spiro compound 73. 

Interest in the organotin derivatives of the acids and thioacids of phosphorus arises from their potential biological action and the wide variety of structures that have been identified by X-ray diffraction. These structures are often particularly complex when the compounds are derived from the partially hydrolyzed mono- or diorganotin compounds, and words such as cubes, drums, crowns, butterflies, clusters, oxygen-capped clusters, and extended clusters have been use to describe them. References to the early work are given in Ref 351, and a recent review is available.352... 

The chemotherapeutic properties, especially the antitumour activities, of diorganotin compounds continue to be the focus of many reports55,56. An interesting compound is... 

In solution, the establishment of cis/trans-D equilibria in hexacoordinate tin complexes is generally fast on the H NMR time scale. A rare observation of different isomers of neutral octahedral diorganotin compounds in solution was described1002. This is somewhat surprising, but may be traced to the usually poor solubility of hexacoordinate organotin compounds, making low-temperature NMR studies difficult if not impossible. 

Complexes 521865, 5221132 and 5231132 are examples of hexacoordinate diorganotin compounds bearing dianionic tridentate 0,N,0-chelating ligands. 

On the basis of the above consideration, diorganotin compounds might be considered to be the ultimate cytotoxic agents and the frequently observed higher activity of triorganotins may be related to their pharmacokinetic behaviour. 

Dioiganotin dihalides are moderately strong Lewis acids and form stable complexes with ammonia and amines. The commercially important diorganotin compounds are most frequently the oxides, carboxylates, and mercaptocarboxylic acid esters. The oxides are amorphous or polycrystalline, highly polymeric, infusible, and insoluble solids. They are moderately strong bases and react readily with a wide variety of strongly and weakly acidic compounds. Their insolubility in all nonreactive solvents makes the choice of proper reaction conditions for such a neutralization reaction an important consideration for optimum yields. 

---